ASE A5 Drum and Disc Brake Service

Question 1

A vehicle with rear drum brakes has a low brake pedal on the first application. The pedal rises and feels firm when it is pumped, and the fluid level and front brakes are normal. Which is the most likely cause?

Accepted Answer

An inoperative drum brake self-adjuster

Answer

Excessive shoe-to-drum clearance means the pedal must travel farther to take up the gap. Pumping the pedal closes that gap and brings the pedal up. A self-adjuster that doesn't work leaves the shoes too far from the drum.

Question 2

A technician measures a brake drum and finds the friction surface is larger than the maximum diameter cast into the drum. What is the correct action?

Accepted Answer

Replace the drum

Answer

The cast discard diameter is the largest safe inside diameter. A drum beyond it has less metal to absorb heat and resist cracking, so it must be replaced.

Question 3

In a duo-servo drum brake with a primary and a secondary shoe, why is the secondary shoe lining typically longer or thicker than the primary shoe lining?

Accepted Answer

The secondary shoe does most of the braking, so it wears more

Answer

In a duo-servo design, the primary shoe drives the secondary shoe into the drum through the adjuster. The secondary shoe therefore handles most of the braking force and wears more.

Question 4

After a brake job, a customer reports squeaking from a rear drum brake during light braking. The linings and drum are new. Which service step was most likely missed?

Accepted Answer

Applying high-temperature brake lubricant to the backing plate shoe contact points

Answer

The shoe edges slide on raised pads on the backing plate. When those contact points are dry or rusty, the shoes stick and chatter, which causes noise. A thin film of high-temperature brake lubricant fixes this.

Question 5

A vehicle has a steering wheel and brake pedal pulsation that appears only during braking and gets worse at highway speeds. The pads and fluid are normal. Which condition is the most likely cause?

Accepted Answer

Disc thickness variation from rotor runout

Answer

Rotor thickness variation makes the pads push back and forth as the rotor turns. This shows up as a pulsing pedal and, on front brakes, steering wheel shake.

ASE A5 Practice Test

ASE A5 Practice Test

ASE A5 Drum and Disc Brake Service